The field of the invention relates generally to railroad systems, and more specifically, to a closed-loop cab signaling monitoring system.
Some known railroad systems use a cab signaling system that communicates track status and information to a locomotive control system from a trackside communications station, wherein the engineer or driver receives information at a display unit onboard the locomotive. Less complex systems may display the trackside signal aspect, i.e. a green, a yellow or a red light, that indicates whether it is safe to proceed, while more sophisticated systems may display speed limits, a location of nearby trains, and/or dynamic information about the track ahead. In some known systems, a speed enforcement system may overlay the cab signaling data for use in warning the driver of a dangerous condition up-track of the locomotive. Moreover, some of such systems may automatically request a braking effort to facilitate stopping the locomotive if the driver ignores or cannot respond to the dangerous condition. Such systems range from simple coded track circuits, to transponders that communicate with the cab, to communication-based train control systems.
Some known train systems experience cab signal “flips” that were the result of a loss of cab signal being decoded at the Onboard System, which then causes a resulting change to a more restrictive aspect, when, for example, the cab signal transmitted into the tracks becomes out-of-specification with respect to signal amplitude, signal period, carrier frequency and/or duty cycle. More specifically, the loss of a decoded cab signal may be due to a malfunction in the trackside communications station, an inadequately maintained trackside communications station, disruption in the track circuit itself (such as a broken rail or changing environmental conditions), a malfunction in the on-board processor, or an inadequately maintained onboard processing system. Some known systems do not include a communication link from the train back to the trackside communications station, and the inaccurate signal remains uncorrected until a maintainer adjusts or corrects the signal at the trackside communications station. Additionally, onboard systems and/or track circuits may go uncorrected as engineers and/or drivers may falsely attribute the cause of the flip to the wayside station.